Physics · Simple pendulum: derivation of expression for its time period
Assertion The bob of a simple pendulum is a ball full of water. If a fine hole i
Assertion The bob of a simple pendulum is a ball full of water. If a fine hole is made in the bottom of the ball, the time period first increases and then decreases. Reason As water flows out of the bob the weight of bob decreases.
- A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
- B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
- C. Assertion is correct but Reason is incorrect
- D. Both Assertion and Reason are incorrect
Step-by-step solution
The time period of a simple pendulum depends on the effective length from the pivot to the center of mass, not on the weight. As water leaks from the bob, the center of mass first moves downward (increasing effective length and time period) then upward back to the center (decreasing effective length and time period), so the assertion is correct. The reason states that weight decreases, which is true but does not affect the time period; thus the reason is correct but not the correct explanation.
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